Transmission apparatus and transmission method of resource assignment information

ABSTRACT

A transmission apparatus comprises an assignment information generator which, in operation, assigns resources on a resource unit (RU) basis to one or more terminal stations (STAs) and generates assignment information that specifies RUs allocated to the one or more STAs; a transmission signal generator which, in operation, generates a transmission signal that includes a legacy preamble, a non-legacy preamble and a data field, wherein the non-legacy preamble comprises a first signal field and a second signal field that carry a set ID and the assignment information, and wherein the set ID identifies one assignment set comprising the one or more STAs and a plurality of assignment indices, and wherein the assignment information comprises a resource assignment indication for each of a plurality of assignment which are referenced by the plurality of assignment indices; and a transmitter which, in operation, transmits the generated transmission signal.

BACKGROUND 1. Technical Field

The present disclosure generally pertains to wireless communicationsand, more particularly, to a method for formatting and transmittingresource assignment information in a wireless communications system.

2. Description of the Related Art

The IEEE (Institute of Electrical and Electronics Engineers) 802.11Working Group is developing 802.11ax HE (High Efficiency) WLAN (WirelessLocal Area Network) air interface in order to achieve a very substantialincrease in the real-world throughput achieved by users in high densityscenarios. OFDMA (Orthogonal Frequency Division Multiple Access)multiuser transmission has been envisioned as one of the most importantfeatures in 802.11ax.

OFDM (Orthogonal Frequency Division Multiplexing) is a multiplexingtechnique that subdivides a system bandwidth into a plurality oforthogonal frequency subcarriers. In OFDM system, an input data streamis divided into several parallel substreams with a lower data rate(accordingly, increased symbol duration), and the substreams aremodulated with respective orthogonal subcarriers and are transmitted.The increased symbol duration improves the robustness of OFDM systemwith respect to the channel delay spread. Further, introduction of a CP(Cyclic Prefix) is able to completely remove intersymbol interference sofar as the CP duration is longer than the channel delay spread. Further,OFDM modulation may be realized by an efficient IFFT (Inverse FastFourier Transform) that makes a plurality of subcarriers usable withlittle complexity. In OFDM system, time and frequency resources aredefined by OFDM symbols in a time domain and subcarriers in a frequencydomain. OFDMA is a multiple access scheme that performs multipleoperations of data streams to and from the plurality of users over thetime and frequency resources of the OFDM system.

Studies are underway to perform frequency scheduling for OFDMA multiusertransmission in 802.11ax. According to frequency scheduling, a radiocommunication access point apparatus (hereinafter simply “access point”)adaptively assigns subcarriers to a plurality of radio communicationstation apparatuses (i.e., terminal apparatus, herein-after simply“stations”) based on reception qualities of frequency bands of thestations (also called as “STAs”). This makes it possible to obtain amaximum multiuser diversity effect and perform communication quiteefficiently.

Frequency scheduling is generally performed based on a Resource Unit(RU). A RU comprises a plurality of consecutive subcarriers. The RUs areassigned by an access point (AP) to each of a plurality of STAs withwhich the AP communicates. The resource assignment result of frequencyscheduling performed by the AP shall be reported to the STAs as resourceassignment information. However, unlike other OFDMA based mobilecommunication standards such as LTE (Long Term Evolution) and WiMAX(Worldwide Interoperability for Microwave Access), 802.11ax is packetoriented and does not support control channels for transmitting resourceassignment information. IEEE Std 802.11ac-2013 is an example of relatedart.

SUMMARY

As flexibility in frequency scheduling increases, more signaling bitsare needed to report the resource assignment information to STAs. Thisresults in an increase of the overhead for reporting resource assignmentinformation. So there is a relationship of trade-off between flexibilityin frequency scheduling and overhead for reporting resource assignmentinformation. A challenge is how to achieve flexible frequency schedulingwhile reducing an increase of the overhead for reporting resourceassignment information.

In one general aspect, the techniques disclosed here feature: atransmission apparatus of the present disclosure comprising a signalgenerator which, in operation, generates a transmission signal thatincludes a legacy preamble, a non-legacy preamble and a data field,wherein the non-legacy preamble comprises a first signal field and asecond signal field, the second signal field including a resourceassignment subfield that indicates a plurality of resource unit (RU)assignments in a frequency domain and a plurality of user-specificsubfields, each carrying per-user allocation information, and wherein asingle RU is allocated to each of the plurality of RU assignments and astart tone index of second one of the plurality of RU assignments islarger than an end tone index of its preceding assignment; and atransmitter which, in operation, transmits the generated transmissionsignal.

With the transmission apparatus and transmission method of resourceassignment information of the present disclosure, it is possible toachieve flexible frequency scheduling while suppressing an increase ofthe overhead for reporting resource assignment information.

It should be noted that general or specific disclosures may beimplemented as a system, a method, an integrated circuit, a computerprogram, a storage medium, or any selective combination thereof.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram illustrating an example format of PPDU accordingto the prior art;

FIG. 2 shows a diagram illustrating an example OFDMA structure of thedata field in case of CBW=20 MHz according to the prior art;

FIG. 3 shows a diagram illustrating an example OFDMA structure of thedata field in case of CBW=40 MHz according to the prior art;

FIG. 4 shows a diagram illustrating an example OFDMA structure of thedata field in case of CBW=80 MHz according to the prior art;

FIG. 5 shows a diagram illustrating an example of continuous resourceallocation in the data field according to the prior art;

FIG. 6 shows a diagram illustrating an example of non-continuousresource allocation in the data field according to the prior art;

FIG. 7 shows a diagram illustrating an example of resource assignmentaccording to a first embodiment of the present disclosure;

FIG. 8A shows a diagram illustrating a first example of resourceassignment indication according to the first embodiment of the presentdisclosure;

FIG. 8B shows a diagram illustrating a second example of resourceassignment indication according to the first embodiment of the presentdisclosure;

FIG. 8C shows a diagram illustrating a third example of resourceassignment indication according to the first embodiment of the presentdisclosure;

FIG. 9 shows a diagram illustrating an example of resource assignmentaccording to a second embodiment of the present disclosure;

FIG. 10A shows a diagram illustrating a first example of resourceassignment indication according to the second embodiment of the presentdisclosure;

FIG. 10B shows a diagram illustrating a second example of resourceassignment indication according to the second embodiment of the presentdisclosure;

FIG. 10C shows a diagram illustrating a third example of resourceassignment indication according to the second embodiment of the presentdisclosure;

FIG. 11 shows a diagram illustrating an example of resource assignmentaccording to a third embodiment of the present disclosure;

FIG. 12A shows a diagram illustrating a first example of resourceassignment indication according to the third embodiment of the presentdisclosure;

FIG. 12B shows a diagram illustrating a second example of resourceassignment indication according to the third embodiment of the presentdisclosure;

FIG. 13 shows a diagram illustrating a signaling of the RU type andposition information according to the third embodiment of the presentdisclosure;

FIG. 14 shows a diagram illustrating example information content ofHE-SIG-A and HE-SIG-B according to the present disclosure;

FIG. 15 shows a diagram illustrating an example sequence of executingOFDMA transmission according to the present disclosure;

FIG. 16 shows a diagram illustrating an example format of Assignment SetID Management frame according to the present disclosure;

FIG. 17 shows a block diagram illustrating an example configuration ofAP according to the present disclosure;

FIG. 18 shows a block diagram illustrating an example configuration ofSTA according to the present disclosure;

FIG. 19 shows a diagram illustrating an example of resource assignmentaccording to a fourth embodiment of the present disclosure;

FIG. 20A shows a diagram illustrating a first example of resourceassignment indication according to the fourth embodiment of the presentdisclosure;

FIG. 20B shows a diagram illustrating a second example of resourceassignment indication according to the fourth embodiment of the presentdisclosure;

FIG. 21 shows a diagram illustrating another example of informationcontent of HE-SIG-A and HE-SIG-B according to the present disclosure;

FIG. 22 shows a diagram illustrating an example structure of HE-SIG-Baccording to the present disclosure;

FIG. 23 shows a flow chart illustrating a method for distributingresource assignment information into HE-SIG-B field according to thepresent disclosure;

FIG. 24 shows a diagram illustrating a first example format of theHE-SIG-B1 or the HE-SIG-B2 in case of CBW=80 MHz;

FIG. 25 shows a diagram illustrating a second example format of theHE-SIG-B1 or the HE-SIG-B2 in case of CBW=80 MHz; and

FIG. 26 shows a diagram illustrating a third example format of theHE-SIG-B1 or the HE-SIG-B2 in case of CBW=80 MHz.

DETAILED DESCRIPTION

Various embodiments of the present disclosure will now be described indetail with reference to the annexed drawings. In the followingdescription, a detailed description of known functions andconfigurations has been omitted for clarity and conciseness.

Underlying Knowledge Forming Basis of the Present Disclosure

FIG. 1 illustrates an example format of PPDU (Physical layer ProtocolData Unit) 100 according to the prior art (see IEEE802.11-15/0132r5,Specification Framework for TGax, May 2015 and IEEE802.11-15/0621r2,Design Principles for HE Preamble, May 2015). The PPDU 100 comprises alegacy preamble 110, a non-legacy preamble (i.e., High Efficiency (HE)preamble) 120 and a data field 130.

The data field 130 carries the payload for one or more STAs. For aspecific STA in terms of single user transmission or a specific group ofSTAs in terms of multiuser MIMO transmission, the payload is carried ona designated resource in units of Resource Unit (RU) spanning aplurality of OFDM symbols. A RU may have different types depending onthe number of constituent subcarriers per RU. OFDM symbols in the datafield 130 shall use a DFT period of 12.8 μs and subcarrier spacing of78.125 kHz. The number of subcarriers per OFDM symbol depends on a sizeof channel bandwidth (CBW). For example, in case of CBW=80 MHz, thenumber of subcarriers per OFDM symbol is 1024. Therefore for a specifictype of RU, the maximum number of RUs per OFDM symbol depends on a sizeof CBW as well.

FIG. 2 illustrates an example OFDMA structure of the data field 130 incase of CBW=20 MHz according to the prior art (see IEEE802.11-15/0132r5,Specification Framework for TGax, May 2015 and IEEE802.11-15/0330r5,OFDMA Numerology and Structure, May 2015). The 20 MHz OFDMA supportsfour types of RUs. The Type I RU comprises 26 consecutive tones and hasa bandwidth of about 2 MHz. The Type II RU comprises 52 consecutivetones and has a bandwidth of about 4.1 MHz. The Type III RU comprises106 consecutive tones and has a bandwidth of about 8.3 MHz. The Type IVRU comprises 242 consecutive tones and has a bandwidth of about 18.9MHz. The maximum number of Type I RUs, Type II RUs, Type III RUs andType IV RUs which the 20 MHz OFDMA is able to support is nine, four, twoand one, respectively. A mix of different types of RUs can beaccommodated in the 20 MHz OFDMA. For example, the 20 MHz OFDMA may bedivided into one Type III RU 202, three Type I RUs 204, 208 and 210 aswell as one Type II RU 206.

FIG. 3 illustrates an example OFDMA structure of the data field 130 incase of CBW=40 MHz according to the prior art (see IEEE802.11-15/0132r5,Specification Framework for TGax, May 2015 and IEEE802.11-15/0330r5,OFDMA Numerology and Structure, May 2015). In addition to Type I RU,Type II RU, Type III RU and Type IV RU, the 40 MHz OFDMA also supportsType V RU, which comprises 484 consecutive tones and has a bandwidth ofabout 37.8 MHz. The maximum number of Type I RUs, Type II RUs, Type IIIRUs, Type IV RUs and Type V RUs which the 40 MHz OFDMA is able tosupport is eighteen, eight, four, two and one, respectively. Similar tothe 20 MHz OFDMA, a mix of different types of RUs can also beaccommodated in the 40 MHz OFDMA.

FIG. 4 illustrates an example OFDMA structure of the data field 130 incase of CBW=80 MHz according to the prior art (see IEEE802.11-15/0132r5,Specification Framework for TGax, May 2015 and IEEE802.11-15/0330r5,OFDMA Numerology and Structure, May 2015). In addition to Type I RU,Type II RU, Type III RU, Type IV RU and Type V RU, the 80 MHz OFDMA alsosupports Type VI RU, which comprises 996 consecutive tones and has abandwidth of about 77.8 MHz. The maximum number of Type I RUs, Type IIRUs, Type III RUs, Type IV RUs, Type V RUs and Type VI RUs which the 80MHz OFDMA is able to support is thirty-seven, sixteen, eight, four, twoand one, respectively. Similar to the 20 MHz or 40 MHz OFDMA, a mix ofdifferent types of RUs can also be accommodated in the 80 MHz OFDMA.

Similar to the 80 MHz OFDMA, the 80+80 MHz OFDMA or 160 MHz OFDMA alsosupports six types of RU, i.e., Type I RU, Type II RU, Type III RU, TypeIV RU, Type V RU and Type VI RU. The maximum number of Type I RUs, TypeII RUs, Type III RUs, Type IV RUs, Type V RUs and Type VI RUs which the80+80 MHz OFDMA or 160 MHz OFDMA is able to support is seventy-four,thirty-two, sixteen, eight, four and two, respectively. Similar to the20 MHz, 40 MHz or 80 MHz OFDMA, a mix of different types of RUs can alsobe accommodated in the 80+80 MHz OFDMA or 160 MHz OFDMA.

Note that use of a Type IV RU in context of 20 MHz OFDMA implies anon-OFDMA configuration, which refers to a case where OFDMA is not usedin the data field 130 of FIG. 1 . That is, the entire bandwidth ofoperation is scheduled for single user transmission or multiuser MIMOtransmission. Similarly, use of a Type V RU in context of 40 MHz OFDMAor a Type VI RU in context of 80 MHz OFDMA implies a non-OFDMAconfiguration. In particular, use of two Type VI RUs in context of 160MHz or 80+80 MHz OFDMA implies a non-OFDMA configuration.

Both continuous resource allocation and non-continuous resourceallocation are possible in OFDMA frequency scheduling.

FIG. 5 illustrates an example of continuous resource allocation in thedata field 130 according to the prior art (see IEEE802.11-15/0330r5,OFDMA Numerology and Structure, May 2015). As shown in FIG. 5 , a singleRU is allocated to a specific STA in terms of single user transmissionor a specific group of STAs in terms of multiuser MIMO transmission inone assignment.

FIG. 6 illustrates an example of non-continuous resource allocation inthe data field 130 according to the prior art (see IEEE802.11-15/0586r1,Frequency Diversity Options in OFDMA, May 2015). In non-continuousresource allocation, more than one RUs which may be not continuous inthe frequency domain can be allocated in one assignment for the purposeof achieving frequency diversity effect. For example, threenon-consecutive RUs 602, 604, and 606 are allocated in one assignment.

With reference to FIG. 1 , the legacy preamble 110 comprises a L-STF(Legacy Short Training Field) 112, a L-LTF (Legacy Long Training Field)114 and a L-SIG (Legacy SIGnal field) 116 in order to keep backwardcompatibility with legacy standard 802.11a/g/n/ac. The L-STF 112 is usedfor start-of-packet detection, AGC (Automatic Gain Control) setting,initial frequency offset estimation and initial time synchronization.The L-LTF 114 is used for further fine frequency offset estimation andtime synchronization. The L-LTF 114 is also used to generate channelestimates for receiving and equalizing the L-SIG 116, HE-SIG-A (HighEfficiency SIGnal A field) 122 and HE-SIG-B (High Efficiency SIGnal Bfield) 124.

The HE preamble 120 comprises a first signal field (i.e., HE-SIG-A) 122,a second signal field (i.e., HE-SIG-B) 124, a HE-STF 126 and a HE-LTF128. The HE-STF 126 is used to retrain AGC. The HE-LTF 128 comprises aplurality of HE-LTF symbols and is used to generate MIMO (Multiple InputMultiple Output) channel estimates for receiving and equalizing the datafield 130. If the PPDU 100 is a DL OFDMA PPDU, both the HE-SIG-A 122 andthe HE-SIG-B 124 contain resource assignment information and userspecific information which are used for each scheduled STA to decode itspayload in the data field 130 at designated resource (seeIEEE802.11-15/0621r2, Design Principles for HE Preamble, May 2015). Ifthe PPDU 100 is a UL OFDMA PPDU, the HE-SIG-A 122 and HE-SIG-B 124 maycontain neither resource assignment information nor user specificinformation since such information is preset by an AP and sent toscheduled STAs via a trigger frame which is carried in the data field ofa previously transmitted DL PPDU (see IEEE802.11-15/0574r0, SIGStructure for UL PPDU, May 2015). Note that both HE-SIG-A 122 andHE-SIG-B 124 shall use a DFT period of 3.2 μs and subcarrier spacing of312.5 kHz in 802.11ax.

Next, various embodiments for resource assignment in frequencyscheduling will be explained in further details.

First Embodiment

FIG. 7 illustrates an example of resource assignment according to afirst embodiment of the present disclosure. The first embodiment isapplicable to continuous resource allocation where one or more RUs thatare consecutive in the frequency domain are allocated in one assignment.In this example, there are eleven assignments in the 80 MHz OFDMA. Eachassignment, which is referenced by an assignment index, is addressed toeither a specific STA in terms of single user transmission or a specificgroup of STAs in terms of multiuser MIMO transmission.

According to the first embodiment, the first assignment has apredetermined start position (e.g., the start tone index of a first RU(e.g., 202 as shown in FIG. 2 ) which is known according to the size ofCBW and the type of the first RU). And a start tone index of asubsequent assignment is next to the end tone index of its precedingassignment (i.e., there is no gap between consecutive assignments). Thetotal number of assignments may be negotiated in advance between anAccess Point (AP) and one or more station apparatus (STAs) or signaledto each STA in the HE-SIG-A field of DL PPDU or the trigger frameexplicitly. However, assume that all available RUs are allocated, a STAcan determine that an assignment is the last assignment if a last RU(e.g., 210 as shown in FIG. 2 ) is allocated in this assignment.Consequently, signaling of the total number of assignments can beomitted

According to the first embodiment, the start position of the firstassignment is predetermined and the start position of a subsequentassignment can be determined from the end position of its precedingassignment. Therefore, it is enough to report the allocation bandwidthfor each assignment. As a result, the overhead due to reporting resourceassignment information for each assignment can be minimized.

According to the first embodiment, the resource assignment informationincludes a plurality of resource assignment indications, each of whichcorresponds to a particular assignment.

FIG. 8A illustrates a first example of resource assignment indicationfor one assignment according to the first embodiment of the presentdisclosure. The resource assignment indication for one assignmentcontains the number of allocated RUs and the type of each of allocatedRUs, from which the allocation bandwidth for the assignment can bederived.

FIG. 8B illustrates a second example of resource assignment indicationfor one assignment according to the first embodiment of the presentdisclosure. In this example, only the same type of RUs can be allocatedin one assignment. The resource assignment indication for the assignmentcontains the number of allocated RUs and the type of allocated RUs, fromwhich the allocation bandwidth for the assignment can be derived.

FIG. 8C illustrates a third example of resource assignment indicationfor one assignment according to the first embodiment of the presentdisclosure. In this example, only a single RU can be allocated in oneassignment. The resource assignment indication for the assignmentcontains the type of allocated RU only, from which the allocationbandwidth for the assignment can be derived.

In the above mentioned examples of the first embodiment, the number ofallocated RUs and the RU type are indicated separately by using bitsignalings.

According to the first embodiment, a two-bit signaling shown in Table 1can be used to indicate the number of allocated RUs. According to Table1, one RU to four RUs can be allocated in one assignment.

TABLE 1 Signaling Number of bits allocated RUs 00 1 01 2 10 3 11 4Additionally, a three-bit signaling shown in Table 2 can be used toindicate the RU type as follows:

TABLE 2 Signaling bits RU Type 000 Type I RU 001 Type II RU 010 Type IIIRU 011 Type IV RU 100 Type V RU 101 Type VI RU 110, 111 Reserved

For example, the type of the RU (Type II RU) allocated in the firstassignment as shown in FIG. 7 can be indicated by “001”.

According to the first embodiment, in case of 20 MHz non-OFDMAtransmission, the number of allocated RUs shall be set to one and thetype of allocated RUs shall be set to Type IV. In case of 40 MHznon-OFDMA transmission, the number of allocated RUs shall be set to oneand the type of allocated RUs shall be set to Type V. In case of 80 MHznon-OFDMA transmission, the number of allocated RUs shall be set to oneand the type of allocated RUs shall be set to Type VI. In case of 80+80MHz or 160 MHz non-OFDMA transmission, the number of allocated RUs shallbe set to two and the type of each of allocated RUs shall be set to TypeVI. In this way, STA shall be able to determine whether an incoming DLPPDU 100 is an OFDMA PPDU or a non-OFDMA PPDU according to the resourceassignment information without any dedicated signaling for such purpose.

Second Embodiment

FIG. 9 illustrates an example of resource assignment according to asecond embodiment of the present disclosure. The second embodiment isalso applicable to continuous resource allocation where one or more RUsthat are consecutive in the frequency domain can be allocated in oneassignment. In this example, there are ten assignments in the 80 MHzOFDMA. Each assignment is addressed to either a specific STA in terms ofsingle user transmission or a specific group of STAs in terms ofmultiuser MIMO transmission.

According to the second embodiment, a start position of the firstassignment may be variable and a gap may exist between consecutiveassignments. In this embodiment, the start tone index of an assignmentis always larger than the end tone index of its preceding assignment.The total number of assignments may be negotiated in advance between anAP and one or more STAs or signaled to each STA in the HE-SIG-A field ofDL PPDU or the trigger frame explicitly.

According to the second embodiment, the start position of the firstassignment is variable and the start position of a subsequent assignmentcannot be derived only from the end position of its precedingassignment. Therefore, in addition to allocation bandwidth, it isnecessary to report start position for each assignment.

According to the second embodiment, the resource assignment informationincludes a plurality of resource assignment indications, each of whichcorresponds to a particular assignment.

FIG. 10A illustrates a first example of resource assignment indicationfor one assignment according to the second embodiment of the presentdisclosure. The resource assignment indication for one assignmentcontains the assignment offset, the number of allocated RUs and the typeof each of allocated RUs. As illustrated in FIG. 9 , for the firstassignment, the assignment offset 902 is relative to the start toneindex of the first Type I RU. For each of the remaining assignments, theassignment offset (e.g., 904) is relative to the end tone index of itspreceding assignment. The start position for a subsequent assignment canbe determined according to the assignment offset and the end tone indexof its preceding assignment. Further, the allocation bandwidth for theassignment can be determined according to the number of allocated RUsand the type of each of allocated RUs.

FIG. 10B illustrates a second example of resource assignment indicationfor one assignment according to the second embodiment of the presentdisclosure. In this example, only the same type of RUs can be allocatedin one assignment. The resource assignment indication for the assignmentcontains the assignment offset, the number of allocated RUs and the typeof allocated RUs. The start position for the assignment can bedetermined according to the assignment offset and the end tone index ofits preceding assignment. Further, the allocation bandwidth for theassignment can be determined according to the number of allocated RUsand the type of allocated RUs.

FIG. 10C illustrates a third example of resource assignment indicationfor one assignment according to the second embodiment of the presentdisclosure. In this example, only a single RU can be allocated in oneassignment. The resource assignment indication for the assignmentcontains the assignment offset and the type of allocated RU. The startposition for the assignment can be determined according to theassignment offset and the end tone index of its preceding assignment.Further, the allocation bandwidth for the assignment can be determinedaccording to the type of allocated RU.

If reception quality of a RU is very poor for all scheduled STAs, the APmay not allocate the RU to them. This RU with poor reception quality isnot used for resource assignment and becomes a gap between twoassignments in this embodiment. The number of unused RUs that form a gapcan be one or plural. As a result, the second embodiment provides moreflexibility in frequency scheduling than the first embodiment. Theoverhead of reporting resource assignment information will slightlyincrease compared to the first embodiment. However, such overheadincrease is not so significant.

In the above mentioned examples of the second embodiment, the assignmentoffset, the number of allocated RUs and the RU type are indicatedseparately by using bit signalings.

According to the second embodiment, if the assignment offset is notlarger than three Type I RUs, a two-bit signaling shown in Table 3 canbe used to indicate the assignment offset in units of the smallest RU(i.e., Type I RU).

TABLE 3 Signaling bits Assignment offset 00 no offset 01 an offset ofone Type I RU 10 an offset of two Type I RUs 11 an offset of three TypeI RUs

For example, for the first assignment as shown in FIG. 9 , theassignment offset 902 (e.g., an offset of two Type I RUs) can beindicated by “10”.

Two-bit signaling shown in Table 1 can be used to indicate the number ofallocated RUs. An alternative two-bit signaling is shown in Table 4.According to Table 4, zero RU to three RUs can be allocated in anassignment. When no RU is allocated in an assignment, the assignment iscalled a “dummy assignment” with zero RU allocation.

TABLE 4 Signaling Number of bits allocated RUs 00 0 01 1 10 2 11 3

Two-bit signaling shown in Table 4 makes it possible to indicate anoffset that is larger than three Type I RUs. For example, if there is anoffset of five Type I RUs between a first assignment and a secondassignment, this offset can be indicated by inserting a “dummyassignment” with zero RU allocation. More specifically, the “dummyassignment” located between the first assignment and the secondassignment has an offset of three RUs and the second assignment has anoffset of two RUs. Then, total offset will be five Type I RUs in thiscase. In addition, two-bit signaling shown in Table 4 can also make itpossible to omit an explicit signaling of the total number ofassignments. For example, if no last RU(s) (e.g., 210 as shown in FIG. 2) is allocated to any STA, a “dummy assignment” with zero RU allocation,which has some offset can be used to indicate such unused resource (RU).In this case, the STA is able to determine that the dummy assignment isthe last assignment.

According to the second embodiment, in case of 20 MHz non-OFDMAtransmission, the number of allocated RUs shall be set to one and thetype of allocated RU shall be set to Type IV. In case of 40 MHznon-OFDMA transmission, the number of allocated RUs shall be set to oneand the type of allocated RU shall be set to Type V. In case of 80 MHznon-OFDMA transmission, the number of allocated RUs shall be set to oneand the type of allocated RU shall be set to Type VI. In case of 80+80MHz or 160 MHz non-OFDMA transmission, the number of allocated RUs shallbe set to two and the type of each of allocated RUs shall be set to TypeVI. In this way, STA shall be able to determine whether incoming DL PPDU100 is an OFDMA PPDU or a non-OFDMA PPDU according to the resourceassignment information without any dedicated signaling for such purpose.

Third Embodiment

FIG. 11 illustrates an example of resource assignment according to athird embodiment of the present disclosure. The third embodiment isapplicable to both continuous resource allocation and non-continuousresource allocation where one or more RUs which may not be consecutivein the frequency domain can be allocated in an assignment. The thirdembodiment enables even more flexibility in frequency scheduling thanthe first embodiment and the second embodiment. In this example, thereare ten assignments in the 80 MHz OFDMA. Each assignment is addressed toeither a specific STA in terms of single user transmission or a specificgroup of STAs in terms of multiuser MIMO transmission.

According to the third embodiment, the total number of assignments maybe negotiated in advance between an AP and one or more STAs, or signaledto each STA in the HE-SIG-A field of DL PPDU or the trigger frameexplicitly.

According to the third embodiment, the resource assignment informationincludes a plurality of resource assignment indications, each of whichcorresponds to a particular assignment.

FIG. 12A illustrates a first example of resource assignment indicationfor one assignment according to the third embodiment of the presentdisclosure. For each assignment, the resource assignment indicationcontains the number of allocated RUs and the type and positioninformation of each of allocated RUs.

FIG. 12B illustrates a second example of resource assignment indicationfor one assignment according to the third embodiment of the presentdisclosure. In this example, only a single RU can be allocated in oneassignment. For the assignment, the resource assignment indicationcontains the type and position information of allocated RU.

According to the third embodiment, the type and position of an allocatedRU are jointly signaled in a single signaling field. That is, a singlesignaling field can be used to indicate both position and type of eachof allocated RUs. FIG. 13 illustrates a signaling of the RU type andposition information according to the third embodiment of the presentdisclosure. Encoding of the RU type and position information isperformed for RUs which 20 MHz OFDMA can support, followed by encodingfor additional RUs which 40 MHz OFDMA can support, encoding foradditional RUs which 80 MHz OFDMA can support, and encoding foradditional RUs which 160 MHz and 80+80 MHz OFDMA can support in thisorder.

In the HE preamble of DL PPDU, assignment information regarding RUs of20 MHz OFDMA is allocated first, followed by assignment informationregarding additional RUs of 40 MHz OFDMA, assignment informationregarding additional RUs of 80 MHz OFDMA, and assignment informationregarding additional RUs of 160 MHz OFDMA in this order. This provides atechnical advantage that a receiver of the resource assignmentinformation (i.e., STA) that only supports CBW=20 MHz has to decode onlya first part (i.e., assignment information regarding RUs of 20 MHzOFDMA) of the resource assignment information, and it can disregard theremaining part of the resource assignment information. Similarly, a STAthat supports CBW=40 MHz has to decode only a first and second parts(i.e., assignment information regarding RUs of 20 MHz OFDMA and 40 MHzOFDMA) of the resource assignment information. Further, a STA thatsupports CBW=80 MHz has to decode a first, second and third parts (i.e.,assignment information regarding RUs of 20 MHz OFDMA, 40 MHz OFDMA and80 MHz OFDMA) of the resource assignment information. Lastly, a STA thatsupports CBW=160 MHz has to decode the resource assignment informationas a whole. In this way, decoding workload at a STA supporting a smallerchannel bandwidth (CBW) can be significantly lowered.

According to the signaling of the RU type and position informationillustrated in FIG. 13 , in one embodiment, an eight-bit signaling isused to indicate the type and position of an allocated RU. So, theoverhead of reporting resource assignment information further increasescompared to the second embodiment. Alternatively, signaling whose lengthis variable depending on CBW may be used. In more details, four-bitsignaling, six-bit signaling, seven-bit signaling and eight-bitsignaling can be used when CBW=20 MHz, CBW=40 MHz, CBW=80 MHz andCBW=80+80 MHz or 160 MHz, respectively. As a result, an increase of theoverhead of reporting resource assignment information due to much moreflexible frequency scheduling is reduced. For example, the type andposition information of the RU allocated to the first assignment of 80MHz OFDMA as illustrated in FIG. 11 can be indicated by “0001010”.

According to the signaling of the RU type and position informationillustrated in FIG. 13 , in order to decode the type and position ofeach of the allocated RUs, a STA supporting CBW up to 20 MHz only needsto maintain a four-bit look up table Likewise, a STA supporting CBW upto 40 MHz only needs to maintain a six-bit look up table and a STAsupporting CBW up to 80 MHz only needs to maintain a seven-bit look uptable. As a result, the memory required for decoding the type andposition information of each of allocated RUs is minimized for STAs withdifferent PHY capabilities in terms of supported CBW.

According to the third embodiment, in case of 20 MHz non-OFDMAtransmission, the number of allocated RUs shall be set to one and thetype and position of allocated RU shall be set to the first Type IV RU.In case of 40 MHz non-OFDMA transmission, the number of allocated RUsshall be set to one and the type and position of allocated RU shall beset to the first Type V RU. In case of 80 MHz non-OFDMA transmission,the number of allocated RUs shall be set to one and the type andposition of allocated RU shall be set to the first Type VI RU. In caseof 80+80 MHz or 160 MHz non-OFDMA transmission, the number of allocatedRUs shall be set to two and the type and position of allocated RUs shallbe set to the first Type VI RU and the second Type VI RU, respectively.Consequently, STA shall be able to determine whether incoming DL PPDU100 is an OFDMA PPDU or a non-OFDMA PPDU according to the resourceassignment information without any dedicated signaling for such purpose.

<HE SIG Field>

FIG. 14 illustrates an example of information content of HE-SIG-A 122and HE-SIG-B 124 of DL PPDU 100 according to the present disclosure.Common control information is included in both the HE-SIG-A fornon-OFDMA transmission and the HE-SIG-A for OFDMA transmission.According to the present disclosure, the information contained in theHE-SIG-A 122 for non-OFDMA transmission differs from the HE-SIG-A 122for OFDMA transmission. In case of non-OFDMA transmission, in additionto the common control information, the HE-SIG-A field 122 containsresource assignment information and user specific information for singleuser transmission or multiuser MIMO transmission. The HE-SIG-B field 124does not exist in case of non-OFDMA transmission in the data field 130.In case of OFDMA transmission in the data field 130, in addition to thecommon control information, the HE-SIG-A field 122 contains resourceassignment indication and user specific information for the firstassignment, and the HE-SIG-B field 124 contains resource assignmentindication and user specific information for each of the remainingassignments.

According to the present disclosure, common control information includesCBW and GI (Guard Interval), etc. The user specific information isrequired for each scheduled STA to decode its payload, e.g., Group ID,Nsts (i.e., the number of space-time streams) and MCS (Modulation andCoding Scheme), etc.

According to the present disclosure, common control information furtherincludes an assignment set ID that maps a plurality of resourceassignments indicated by resource assignment information to scheduledSTAs, which will be detailed later. As a result, after decoding HE-SIG-A122 of a DL PPDU 100, if a STA determines that it is not addressed bythe PPDU 100, it will ignore the remaining of the PPDU 100 and reduceits power consumption.

According to the present disclosure, the common control information mayfurther include an Allocation Defined flag in conjunction with theassignment set ID. Assume a first DL PPDU and a subsequent second DLPPDU are associated with the same assignment set ID. The AllocationDefined flag of the second DL PPDU shall be set if the resourceassignment information contained in the first DL PPDU can be reused bythe second DL PPDU. In that case, the resource assignment informationfor the second DL PPDU can be omitted, and thus signaling overhead canbe reduced.

According to the present disclosure illustrated in FIG. 14 , theHE-SIG-A 122 contains similar information for non-OFDMA transmission andOFDMA transmission in the data field 130. This would reduceimplementation complexity of STA.

According to the present disclosure illustrated in FIG. 14 , whennon-OFDMA transmission is performed in the data field 130, the HE-SIG-B124 does not exist. As a result, STAs need not to decode HE-SIG-B 124,which leads to a reduced power consumption of STAs.

<Radio Communication System>

FIG. 15 illustrates an example sequence of executing OFDMA transmissionin a radio communication system according to the present disclosure. Theradio communication system comprises an AP 1502 and a plurality of STAs(e.g., 1504) which are associated with AP 1502. AP 1502 performsfrequency scheduling using the plurality of RUs in the radiocommunication system.

Prior to initiation of DL OFDMA transmission, AP 1502 determinespossible combinations of STAs that can be addressed by a DL OFDMA PPDUby assigning STAs to DL assignment sets and to specific assignmentindices within those sets. One assignment set is identified by anassignment set ID and refers to a plurality of STAs and a plurality ofassignment indices where each of the plurality of assignment indices isaddressed to one or more of the plurality of STAs. For example, oneassignment set comprises two STAs (STA1 and STA2) and two assignmentswhere the first assignment is addressed to STA1 and the secondassignment is addressed to STA2. Then AP 1502 transmits an AssignmentSet ID Management frame 1510 to STA 1504 to assign or change itsassignment indices corresponding to one or more DL assignment sets ofwhich STA 1504 is a member.

Prior to initiation of UL OFDMA transmission, AP 1502 determines thepossible combinations of STAs that transmit a UL OFDMA PPDU by assigningSTAs to UL assignment sets and to specific assignment indices withinthose sets. Then AP 1502 transmits an Assignment Set ID Management frame1512 to STA 1504 to assign or change its assignment indicescorresponding to one or more UL assignment sets of which STA 1504 is amember.

FIG. 16 illustrates an example format of Assignment Set ID Managementframe 1510 or 1512 according to the present disclosure. The frame 1510comprises a Directionality field 1622, a Membership Status Array field1624 and an Assignment Index Array field 1626. The Directionality field1622 indicates whether OFDMA assignment sets are for DL or UL. STA 1504may be assigned to multiple sets by setting multiple subfields of theMembership Status Array field 1624 to 1 in the frame 1510. An assignmentindex in each assignment set of which STA 1504 is a member is indicatedby the associated subfield in the Assignment Index Array field 1626 inthe frame 1510. For each Set ID, AP 1502 may assign the same assignmentindex to multiple STAs. STA 1504 shall have only one assignment index ineach set of which it is a member.

According to the present disclosure, the AP 1502 may transmit theAssignment Set ID management frames to STA 1504 when it associates withthe AP 1502. In addition, the AP 1502 may transmit the Assignment Set IDmanagement frames to STA 1504 periodically or if necessary.

If only a specific combination of STAs is allowed to communicate withthe AP 1502 in an OFDMA transmission for a period of time, a simplemanagement frame can be used instead of the Assignment Set ID managementframe to indicate an assignment index for each STA. In this case, theassignment set ID in the HE-SIG-A of DL PPDU or the trigger frame can beomitted.

If AP 1502 has buffered data addressed to STA 1504, AP 1502 selects a DLassignment set of which STA 1504 is a member and determines DL resourcerequired to transmit the data addressed to STA 1504 based on the datasize and QoS (Quality of Service) requirement. Then AP 1502 transmits aDL OFDMA PPDU 1514 which includes the data addressed to STA 1504,assignment set ID of the selected DL assignment set as well as othercontrol information (e.g., resource assignment information) which isrequired by STA 1504 to decode its data inside the DL OFDMA PPDU 1514.Note that when a subsequent DL OFDMA PPDU which includes the sameassignment set ID as the DL OFDMA PPDU 1514 is transmitted, if theresource assignment information contained in the DL OFDMA PPDU 1514 canbe reused by the subsequent DL OFDMA PPDU, the Allocation Defined flagin the subsequent DL OFDMA PPDU shall be set and then resourceassignment information needs not to be included in the subsequent DLOFDMA PPDU.

If STA 1504 has buffered data addressed to AP 1502, STA 1504 may performADDTS Request/Response frame exchange 1516 with AP 1502 to requesttransmission bandwidth for its data. ADDTS Request frame may alsoinclude information on RUs, for example, channel quality information toshow which RUs are preferable or not preferable for the STA 1504. ThenAP 1502 selects a UL assignment set of which STA 1504 is a member anddetermines UL resource according to the requested transmission bandwidthby STA 1504. After that, AP 1502 transmits a trigger frame 1518 to STA1504 which includes assignment set ID of the selected UL assignment setas well as other control information (e.g., resource assignmentinformation) which is required by STA 1504 to transmit its data. Notethat when a subsequent trigger frame which includes the same assignmentset ID as the trigger frame 1518 is transmitted, if the resourceassignment information contained in the trigger frame 1518 can be reusedby the subsequent trigger frame, the Allocation Defined flag in thesubsequent trigger frame shall be set and then resource assignmentinformation needs not to be included in the subsequent trigger frame.The trigger frame may also include UL transmission power controlinformation and UL transmission duration information. After receivingthe trigger frame 1518, STA 1504 transmits a UL OFDMA PPDU 1520 to sendits data using the designated resource accordingly. STA 1504 may controlits transmission power based on the transmission power controlinformation so that, at the AP 1502, large variation between receptionpower from each STA can be avoided.

<Configuration of an Access Point>

FIG. 17 is a block diagram illustrating example configuration of AP 1502according to the present disclosure. The AP 1502 comprises a controller1702, a scheduler 1704, a message generator 1708, a message processor1706, a PHY processor 1710 and an antenna 1712. The controller 1702 is aMAC protocol controller and controls general MAC protocol operations.

For DL OFDMA transmission, scheduler 1704 performs frequency schedulingunder the control of the controller 1702 based on channel qualityindicators (CQIs) from STAs and assigns data for STAs to RUs. Examplesof a CQI-based scheduling method include the Max CIR method and theproportional-fairness method. Scheduler 1704 also outputs the resourceassignment results to the message generator 1708. The message generator1708 generates corresponding common control information, resourceassignment information, user specific information and data for scheduledSTAs, which are formulated by the PHY processor 1710 into an OFDMA PPDUand transmitted through the antenna 1712. The resource assignmentinformation can be configured according to the above mentionedembodiments. On the other hand, the message processor 1706 analyzes thereceived CQIs from STAs through the antenna 1712 under the control ofthe controller 1702 and provides them to scheduler 1704 and controller1702. These CQIs are received quality information reported from theSTAs. Further, each STA can measure received quality on a per RU basisusing the received SNR, received SIR, received SINR, received CINR,received power, interference power, bit error rate, throughput and MCSwhereby a predetermined error rate can be achieved. Furthermore, the CQImay also be referred to as “CSI” (Channel State Information).

For UL OFDMA transmission, scheduler 1704 performs frequency schedulingunder the control of the controller 1702 based on transmission bandwidthrequest from STAs and assigns resource for scheduled STAs for UL datatransmission. At the same time, scheduler 1704 may also perform timescheduling to determine duration of UL OFDMA frame or transmissionopportunity (TXOP) in which STAs have a right to perform UL OFDMA frameexchanges. Scheduler 1704 also outputs the resource assignment resultsto the message generator 1708. The message generator 1708 generates atrigger frame including common control information, resource assignmentinformation and user specific information, which is formulated by thePHY processor 1710 into a DL PPDU and transmitted through the antenna1712. On the other hand, the message processor 1706 analyzes thereceived transmission bandwidth request from STAs through the antenna1712 and provides them to scheduler 1704 and controller 1702. Theantenna 1712 can be comprised of one antenna port or a combination of aplurality of antenna ports.

<Configuration of a STA>

FIG. 18 is a block diagram illustrating example configuration of STA1504 according to the present disclosure. STA 1504 comprises acontroller 1802, a message generator 1804, a message processor 1806, aPHY processor 1808 and an antenna 1810. The controller 1802 is a MACprotocol controller and controls general MAC protocol operations. Theantenna 1810 can be comprised of one antenna port or a combination of aplurality of antenna ports.

For UL OFDMA transmission, the message processor 1806 analyzes thereceived trigger frame from AP 1502 through the antenna 1810 andprovides common control information, resource assignment information anduser specific information to controller 1802. The resource assignmentinformation can be configured according to the above mentionedembodiments. The message generator 1804 generates data under the controlof the controller 1802, which are formulated by the PHY processor 1808under the control of the controller 1802 into an UL OFDMA PPDU in such away that the data is transmitted at the designated resource. The ULOFDMA PPDU is transmitted through the antenna 1810.

For DL OFDMA transmission, the message processor 1806 estimates channelquality from the received DL PPDU through the antenna 1810 and providesthem to controller 1802. The message generator 1804 generates CQImessage, which is formulated by the PHY processor 1808 into an UL PPDUand transmitted through the antenna 1810.

Fourth Embodiment

FIG. 19 illustrates an example of resource assignment according to afourth embodiment of the present disclosure. The fourth embodiment isapplicable to continuous resource allocation where one or more RUs thatare consecutive in the frequency domain can be allocated in oneassignment. In this example, there are nine assignments (#0 to #9) inthe 80 MHz OFDMA. Each assignment is addressed to either a specific STAin terms of single user transmission or a specific group of STAs interms of multiuser MIMO transmission.

According to the fourth embodiment, the total number of assignments maybe negotiated in advance between an AP and one or more STAs or may beexplicitly signaled to each STA in the HE-SIG-A field of DL PPDU or thetrigger frame.

Unlike the first and second embodiments where the start tone index of anassignment is always larger than the end tone index of its precedingassignment, there is no such restriction in the fourth embodiment. Thestart tone index and the end tone index of an assignment can be smallerthan the first tone index of another preceding assignment. As a result,the scheduling flexibility is improved in the fourth embodiment.

According to the fourth embodiment, the resource assignment informationincludes a plurality of resource assignment indications, each of whichcorresponds to a particular assignment.

FIG. 20A illustrates a first example of resource assignment indicationfor one assignment according to the fourth embodiment of the presentdisclosure. The resource assignment indication for one assignmentcontains the number of allocated RUs, the position and type of the firstallocated RU and the type of each of remaining allocated RUs. In otherwords, each resource assignment indication contains position and typeinformation of the first RU only and type information of each of theremaining RUs. The start position for an assignment can be determinedaccording to the position of the first allocated RU. Further, theallocation bandwidth for the assignment can be determined according tothe number of allocated RUs and the type of each of allocated RUs.

FIG. 20B illustrates a second example of resource assignment indicationfor one assignment according to the fourth embodiment of the presentdisclosure. In this example, only the same type of RUs can be allocatedin one assignment. The resource assignment indication for the assignmentcontains the number of allocated RUs and the position and type of thefirst allocated RU. The start position for an assignment can bedetermined according to the position of the first allocated RU. Further,the allocation bandwidth for the assignment can be determined accordingto the number of allocated RUs and the type of the first allocated RU.

Two-bit signaling shown in Table 1 can be used to indicate the number ofallocated RUs, and three-bit signaling shown in Table 2 can be used toindicate the RU type. The type and position of the first allocated RUcan be jointly signalled in a single signaling field as illustrated inFIG. 13 .

[HE SIG Field]

FIG. 21 illustrates another example of information content of HE-SIG-A122 and HE-SIG-B 124 of DL PPDU according to the present disclosure.According to the present disclosure, the HE-SIG-B field 124 does notexist in the DL PPDU in case of single user transmission. In case ofmultiuser transmission, the HE-SIG-B field 124 exists in the DL PPDU andcontains resource assignment information (i.e., resource assignmentindication for each assignment), followed by user specific informationfor each assignment. The HE-SIG-B field 124 is encoded on a per 20 MHzsubband basis. For CBW=40 MHz, 80 MHz, 160 MHz or 80+80 MHz, the numberof 20 MHz subbands carrying different content is two.

An example structure of the HE-SIG-B field 124 in FIG. 21 in case ofCBW=80 MHz is illustrated in FIG. 22 . The HE-SIG-B field 124 comprisestwo portions: HE-SIG-B1 2202 and HE-SIG-B2 2204. The HE-SIG-B1 2202 istransmitted over the first 20 MHz subband channel 2222 and a duplicateof the HE-SIG-B 2202 is transmitted over the third 20 MHz subbandchannel 2226 while the HE-SIG-B2 2204 is transmitted over the second 20MHz subband channel 2224 and a duplicate of the HE-SIG-B2 2204 istransmitted over the fourth 20 MHz subband channel 2228.

According to the present disclosure, resource assignment indication forone assignment that is fully located within a 20 MHz subband channelshould be carried in one of the HE-SIG-B1 2202 and HE-SIG-B2 2204 thatis transmitted over the same 20 MHz subband channel. In more details,the HE-SIG-B1 2202 should carry resource assignment indications for theassignments (e.g., 2212) that are fully located within the first 20 MHzsubband channel 2222 or the third 20 MHz subband channel 2226. TheHE-SIG-B2 2204 should carry resource assignment indications for theassignments (e.g., 2218) that are fully located within the second 20 MHzsubband channel 2224 or the fourth 20 MHz subband channel 2228. In thisway, even if control signaling in a 20 MHz subband channel (e.g., 2222or 2226) is corrupted due to interference, the DL PPDU in another 20 MHzsubband channel (e.g., 2224 or 2228) can be decoded correctly.

According to the present disclosure, for the assignments (e.g., 2216)that span across two or more neighboring 20 MHz subband channels, thecorresponding resource assignment indications can be carried either inthe HE-SIG-B1 2202 or in the HE-SIG-B2 2204 such that data amount of theHE-SIG-B1 2202 and data amount of the HE-SIG-B2 2204 become similar insize. Since smaller one of the HE-SIG-B1 and the HE-SIG-B2 will beappended padding bits until their payload sizes become the same, thepadding efficiency of HE-SIG-B field can be improved or maximizedaccording to this embodiment.

FIG. 23 is a flow chart illustrating a method for distributing resourceassignment information into the HE-SIG-B field according to the presentdisclosure. The method shown in FIG. 23 starts at Step 2302. At Step2304, resource assignment indications for the assignments that are fullylocated in any 20 MHz subband channel over which the HE-SIG-B1 istransmitted are included (i.e., mapped) in the HE-SIG-B1. At Step 2306,resource assignment indications for the assignments that are fullylocated in any 20 MHz subband channel over which the HE-SIG-B2 istransmitted are included (i.e., mapped) in the HE-SIG-B2. Note that thesequential order of Step 2304 and Step 2306 may be interchangeable. AtStep 2308, resource assignment indications for the assignments that spanacross two or more neighboring 20 MHz subband channels are included(i.e., mapped) in either the HE-SIG-B1 or the HE-SIG-B2 so that dataamount of the HE-SIG-B1 and data amount of the HE-SIG-B2 become similarin size. This method stops at Step 2310.

Take the following case as an example:

CBW=40 MHz;

Four assignments: A1, A2, A3 and A4;

Assignment A1 contains one or more RUs that are located in the lower 20MHz subband channel over which the HE-SIG-B1 is transmitted;

Each of assignments A2 and A3 contains one or more RUs that are locatedin the upper 20 MHz subband channel over which the HE-SIG-B2 istransmitted;

Assignment A4 contains one or more RUs that span across both of thelower and the upper 20 MHz subband channels; and

Assume that resource assignment indication for each of four assignmentsrequires the similar number of information bits.

According to the method illustrated in FIG. 23 , resource assignmentindications for the above four assignments should be distributed intothe HE-SIG-B as follows:

Resource assignment indication for assignment A1 is signaled in theHE-SIG-B1;

Resource assignment indications for assignments A2 and A3 are signaledin the HE-SIG-B2; and

Resource assignment indication for assignment A4 is signaled in theHE-SIG-B1.

By distributing resource assignment indications between the HE-SIG-B1and the HE-SIG-B2, data amount of the HE-SIG-B1 and data amount of theHE-SIG-B2 become similar in size, thus improving padding efficiency inthe HE-SIG-B field.

[HE-SIG-B Field]

FIG. 24 illustrates a first example format of the HE-SIG-B1 2202 or theHE-SIG-B2 2204 in FIG. 22 in case of CBW=80 MHz. The HE-SIG-B1 2202 orthe HE-SIG-B2 2204 comprises a common field 2410 and a user-specificfield 2450. The common field 2410 comprises a first resource assignmentsubfield 2412, a second resource assignment subfield 2414, a CRC (CyclicRedundancy Check) subfield 2418 and a tail bits subfield.

In context of the HE-SIG-B1 2202, the first resource assignment subfield2412 contains a RU arrangement pattern index which indicates a specificRU arrangement in the frequency domain (including MU-MIMO (MultiuserMultiple Input Multiple Output) related information) for the first 20MHz subband channel 2222 in FIG. 22 . The mapping of RU arrangementpattern indices and the corresponding RU arrangement patterns ispredetermined. An example mapping of RU arrangement pattern indices andthe corresponding RU arrangement patterns is shown in Table 5. Note thatRUs are arranged from lower frequency to higher frequency in thefrequency domain within a 20 MHz subband channel and Type I RUs and TypeII RUs can be used for SU-MIMO transmission only.

TABLE 5 RU Arrange- ment Pattern Index RU Arrangement Pattern 0 9 Type IRUs 1 1 Type II RU, followed by 7 Type I RUs 2 2 Type I RUs, followed by1 Type II RU and 5 Type I RUs 3 5 Type I RUs, followed by 1 Type II RUand 2 Type I RUs 4 7 Type I RUs, followed by 1 Type II RU 5 2 Type IIRUs, followed by 5 Type I RUs 6 1 Type II RU, followed by 3 Type I RUs,1 Type II RU and 2 Type I RUs 7 1 Type II RU, followed by 5 Type I RUsand 1 Type II RU 8 2 Type I RUs, followed by 1 Type II RU, 1 Type I RU,1 Type II RU and 2 Type I RUs 9 2 Type I RUs, followed by 1 Type II RU,3 Type I RUs and 1 Type II RU 10 5 Type I RUs, followed by 2 Type II RUs11 2 Type II RUs, followed by 1 Type I RU, 1 Type II RU and 2 Type I RUs12 2 Type II RUs, followed by 3 Type I RUs and 1 Type II RU 13 1 Type IIRU, followed by 3 Type I RUs and 2 Type II RUs 14 2 Type I RUs, followedby 1 Type II RU, 1 Type I RU and 2 Type II RUs 15 2 Type II RUs,followed by 1 Type I RU and 2 Type II RUs 16 1 Type III RU for SU-MIMOtransmission, followed by 5 Type I RUs 17 1 Type III RU for SU-MIMOtransmission, followed by 3 Type I RUs and 1 Type II RU 18 1 Type III RUfor SU-MIMO transmission, followed by 1 Type I RU, 1 Type II RU and 2Type I RUs 19 1 Type III RU for SU-MIMO transmission, followed by 1 TypeI RU and 2 Type II RUs 20 1 Type III RU for SU-MIMO transmission,followed by 1 Type I RU and 1 Type III RU for SU-MIMO transmission 21 5Type I RUs, followed by 1 Type III RU for SU-MIMO transmission 22 1 TypeII RU, followed by 3 Type I RUs and 1 Type III RU for SU-MIMOtransmission 23 2 Type I RUs, followed by 1 Type II RU, 1 Type I RU and1 Type III RU for SU-MIMO transmission 24 2 Type II RUs, followed by 1Type I RU and 1 Type III RU for SU-MIMO transmission 25 5 Type I RUs,followed by 1 Type III RU for MU-MIMO transmission with 2 usersmultiplexed 26 5 Type I RUs, followed by 1 Type III RU for MU-MIMOtransmission with 3 users multiplexed 27 5 Type 1 RUs, followed by 1Type ill RU for MU-MIMO transmission with 4 users multiplexed 28 5 Type1 RUs, followed by 1 Type III RU for MU-MIMO transmission with 5 usersmultiplexed 29 5 Type 1 RUs, followed by 1 Type III RU for MU-MIMOtransmission with 6 users multiplexed 30 5 Type I RUs, followed by 1Type III RU for MU-MIMO transmission with 7 users multiplexed 31 5 TypeI RUs, followed by 1 Type III RU for MU-MIMO transmission with 8 usersmultiplexed . . . . . .

With reference to Table 1, for example, the first resource assignmentsubfield 2412 may contain a RU arrangement pattern index 25 to indicatea specific RU arrangement for the first 20 MHz subband channel wherefive Type I RUs followed by one Type III RU in the frequency domain, andeach of five Type I RUs is used for SU-MIMO (Single User Multiple InputMultiple Output) transmission while the Type III RU is used for MU-MIMOtransmission with two users multiplexed. The second resource assignmentsubfield 2414 indicates the RU arrangement in the frequency domain andMU-MIMO related information for the third 20 MHz subband channel 2226 inFIG. 22 .

In context of the HE-SIG-B2 2204, the first resource assignment subfield2412 indicates the RU arrangement in the frequency domain and MU-MIMOrelated information for the second 20 MHz subband channel 2224 in FIG.22 . The second resource assignment subfield 2414 indicates the RUarrangement in the frequency domain and MU-MIMO related information forthe fourth 20 MHz subband channel 2228 in FIG. 22 . It should be notedthat the RU arrangement signaled by the first resource assignmentsubfield 2412 and the second resource assignment subfield 2414 does notinvolve the center Type I RU 402 as illustrated in FIG. 4 , which islocated between two adjacent 20 MHz subband channels.

The user-specific field 2450 comprises a plurality of BCC (BinaryConvolutional Coding) blocks 2460. Each of the BCC blocks 2460 exceptthe last BCC block 2460-N comprises a first user-specific subfield, asecond user-specific subfield, a CRC subfield and a tail bits subfield.The last BCC block 2460-N may comprise a single user-specific subfield.Each of user-specific subfields in the user-specific field 2450 carriesper-user allocation information (e.g., STA identifier for addressing andthe information necessary for decoding the PPDU 100 such as the numberof spatial streams and modulation and coding scheme, etc). For each RUassigned for SU-MIMO transmission, there is only a single correspondinguser-specific subfield. For each RU assigned for MU-MIMO transmissionwith K users multiplexed, there are K corresponding user-specificsubfields. The ordering of user-specific subfields in the user-specificfield 2450 is compliant with the RU arrangement signaled by the firstresource assignment subfield 2412 and the second resource assignmentsubfield 2414.

According to the present disclosure, one of the user-specific subfieldsof the user-specific field 2450 in each of the HE-SIG-B1 2022 and theHE-SIG-B2 2024 is used to carry per-user allocation information for thecenter Type I RU 402 as illustrated in FIG. 4 . The user-specificsubfield for the center Type I RU shall be located at a predeterminedposition in the user-specific field 2450. For example, the user-specificsubfield for the center Type I RU is the last user-specific subfield2470 in the user-specific field 2450.

According to the present disclosure, the number of the user-specificsubfields in the user-specific field 2450 except the user-specificsubfield for the center Type I RU can be derived from the first resourceassignment subfield 2412 and the second resource assignment subfield2414 in the common field 2410.

In case of CBW=160 MHz or 80+80 MHz, there is a center Type I RU that islocated between two adjacent 20 MHz subband channels for every 80 MHz.As a result, there are two center Type-I RUs in total in case of CBW=160MHz or 80+80 MHz. In this case, according to the present disclosure, twoof the user-specific subfields of the user-specific field 2450 in eachof the HE-SIG-B1 2022 and the HE-SIG-B2 2024 are used to carry per-userallocation information for the two center Type I RUs, respectively. Eachof the two user-specific subfields for the center Type I RUs shall belocated at a predetermined position in the user-specific field 2450. Forexample, the user-specific subfield for a first center Type I RU is thelast user-specific subfield in the user-specific field 2450 while theuser-specific subfield for a second center Type I RU is the second lastuser-specific subfield in the user-specific field 2450.

FIG. 25 illustrates a second example format of the HE-SIG-B1 2202 or theHE-SIG-B2 2204 in FIG. 22 in case of CBW=80 MHz. The HE-SIG-B1 2202 orthe HE-SIG-B2 2204 comprises a common field 2510 and a user-specificfield 2550. The common field 2510 comprises a first resource assignmentsubfield 2512, a second resource assignment subfield 2514, a presence ofallocation information for center RU subfield 2516, a CRC subfield 2518and a tail bits subfield. The user-specific field 2550 comprises aplurality of BCC blocks 2560. Each of the BCC blocks 2560 except thelast BCC block 2560-N comprises a first user-specific subfield, a seconduser-specific subfield, a CRC subfield and a tail bits subfield. Thelast BCC block 2560-N may comprise a single user-specific subfield. Eachof the user-specific subfields in the user-specific field 2450 carriesper-user allocation information.

The first resource assignment subfield 2512, the second resourceassignment subfield 2514 and each of user-specific subfields are definedin the same way as their respective counterparts in FIG. 24 .

According to the present disclosure, the presence of allocationinformation for center RU subfield 2516 in the common field 2510 is usedto indicate whether there is a user-specific subfield for the centerType I RU in the user-specific field 2550. If a user-specific subfieldfor the center Type I RU is present in the user-specific field 2550, itsposition in the user-specific field 2550 shall be predetermined. Forexample, the user-specific subfield for the center Type I RU is the lastuser-specific subfield 2570 in the user-specific field 2550.

According to the present disclosure, the number of user-specificsubfields in the user-specific field 2550 can be derived from the firstresource assignment subfield 2512, the second resource assignmentsubfield 2514 and the presence of allocation information for center RUsubfield 2516 in the common field 2510.

Compared with the first example format of the HE-SIG-B1 2202 or theHE-SIG-B2 2204 as illustrated in FIG. 24 where the user-specificsubfield for the center Type I RU is included in both the HE-SIG-B1 2202and the HE-SIG-B2 2204, the second example format as illustrated in FIG.25 enables more flexible arrangement of user-specific subfield for thecenter Type I RU in the HE-SIG-B1 2202 and the HE-SIG-B2 2204. For oneexample, the user-specific subfield for the center Type I RU may beincluded in either of the HE-SIG-B1 2202 and the HE-SIG-B2 2204 for thepurpose of keeping load balancing between the HE-SIG-B1 2202 and theHE-SIG-B2 2204 and improving channel efficiency. In other words, theuser-specific subfield for the center Type I RU may be included ineither of the HE-SIG-B1 2202 and the HE-SIG-B2 2204 so that thedifference in terms of the number of user-specific subfields between theHE-SIG-B1 2202 and the HE-SIG-B2 2204 is minimized. For another example,the user-specific subfield for the center Type I RU may be included inboth of the HE-SIG-B1 2202 and the HE-SIG-B2 2204 for the purpose ofimproving reliability for decoding the user-specific subfield for thecenter Type I RU.

In case of CBW=160 MHz or 80+80 MHz, the presence of allocationinformation for center RU subfield 2516 in the common field 2510 needsto indicate whether there is a user-specific subfield for each of thetwo center Type I RUs in the user-specific field 2550. If theuser-specific subfield for only one of the two center Type I RUs ispresent in the user-specific field 2550, its position in theuser-specific field 2550 shall be predetermined. For example, theuser-specific subfield for the center Type I RU is the lastuser-specific subfield in the user-specific field 2550. If theuser-specific subfield for each of the two center Type I RUs is presentin the user-specific field 2550, the two user-specific subfields for thecenter Type I RUs shall be located at the predetermined positions in theuser-specific field 2550. For example, the user-specific subfield for afirst center Type I RU is the last user-specific subfield in theuser-specific field 2550 while the user-specific subfield for a secondcenter Type I RU is the second last user-specific subfield in theuser-specific field 2550.

FIG. 26 illustrates a third example format of the HE-SIG-B1 2202 or theHE-SIG-B2 2204 in FIG. 22 in case of CBW=80 MHz. The HE-SIG-B1 2202 orthe HE-SIG-B2 2204 comprises a common field 2610 and a user-specificfield 2650. The common field 2610 comprises a first resource assignmentsubfield 2612, a second resource assignment subfield 2614, a CRCsubfield 2618 and a tail bits subfield. The user-specific field 2650comprises a plurality of BCC blocks 2660. Each of BCC blocks 2660 exceptthe last BCC block 2660-N comprises a first user-specific subfield, asecond user-specific subfield, a CRC subfield and a tail bits subfield.The last BCC block 2660-N may comprise a single user-specific subfield.Each of user-specific subfields in the user-specific field 2650 carriesper-user allocation information.

The first resource assignment subfield 2612, the second resourceassignment subfield 2614 and each of user-specific subfields are definedin the same way as their respective counterparts in FIG. 24 .

According to the present disclosure, whether the CRC subfield 2618 inthe common field 2610 is masked by a predefined binary sequence (i.e.,whether a XOR (Exclusive OR) is applied to the CRC subfield 2618 and apredefined binary sequence) is used to indicate whether there is auser-specific subfield for the center Type I RU in the user-specificfield 2650. For example, if the CRC subfield 2618 in the common field2610 is not masked with a predefined binary sequence, there is nouser-specific subfield for the center Type I RU in the user-specificfield 2650. Otherwise there is a user-specific subfield for the centerType I RU in the user-specific field 2650.

Alternatively, instead of the CRC subfield 2618 in the common field2610, whether the CRC subfield of a specific BCC block in theuser-specific field 2650 is masked by a predefined binary sequence isused to indicate whether there is a user-specific subfield for thecenter Type I RU in the user-specific field 2650. For example, if theCRC subfield 2666 of the first BCC block 2660-1 is not masked by apredefined binary sequence, there is no user-specific subfield for thecenter Type I RU in the user-specific field 2650. Otherwise there is auser-specific subfield for the center Type I RU in the user-specificfield 2650.

If a user-specific subfield for the center Type I RU is present in theuser-specific field 2650, its position in the user-specific field 2650shall be predetermined. For example, the user-specific subfield for thecenter Type I RU is the last user-specific subfield 2670 in theuser-specific field 2650.

According to the present disclosure, the number of user-specificsubfields in the user-specific field 2650 except the user-specificsubfield for the center Type I RU can be derived from the first resourceassignment subfield 2612 and the second resource assignment subfield2614 in the common field 2610.

Compared with the second example format of the HE-SIG-B1 2202 or theHE-SIG-B2 2204 as illustrated in FIG. 25 , the third example format asillustrated in FIG. 26 does not need a signaling subfield in the commonfield to signal the presence of user-specific subfield for the centerType I RU in the user-specific field. In other words, the signaling bitsrequired by the third example format is reduced compared with the secondexample format.

In case of CBW=160 MHz or 80+80 MHz, whether the CRC subfield 2618 inthe common field 2610 (or the CRC subfield 2666 in the user-specificfield 2650) is masked by one of the three predefined binary sequences isused to indicate whether there is a user-specific subfield for each ofthe two center Type I RUs in the user-specific field 2650. For example,if the CRC subfield 2618 in the common field 2610 (or the CRC subfield2666 in the user-specific field 2650) is not masked by one of threepredefined binary sequences, there is no user-specific subfield for thecenter Type I RU in the user-specific field 2650. If the CRC subfield2618 in the common field 2610 (or the CRC subfield 2666 in theuser-specific field 2650) is masked by a first predefined binarysequence, there is a user-specific subfield for a first center Type I RUin the user-specific field 2650. If the CRC subfield 2618 in the commonfield 2610 (or the CRC subfield 2666 in the user-specific field 2650) ismasked by a second predefined binary sequence, there is a user-specificsubfield for a second center Type I RU in the user-specific field 2650.If the CRC subfield 2618 in the common field 2610 (or the CRC subfield2666 in the user-specific field 2650) is masked by a third predefinedbinary sequence, there is a user-specific subfield for each of the twocenter Type I RUs in the user-specific field 2650. If the user-specificsubfield for only one of the two center Type I RUs is present in theuser-specific field 2650, its position in the user-specific field 2650shall be predetermined. For example, the user-specific subfield for thecenter Type I RU is the last user-specific subfield in the user-specificfield 2650. If the user-specific subfield for each of the two centerType I RUs is present in the user-specific field 2650, the twouser-specific subfields for the center Type I RUs shall be located atthe predetermined positions in the user-specific field 2650. Forexample, the user-specific subfield for a first center Type I RU is thelast user-specific subfield in the user-specific field 2650; while theuser-specific subfield for a second center Type I RU is the second lastuser-specific subfield in the user-specific field 2650.

In the foregoing embodiments, the present disclosure is configured withhardware by way of example, but the disclosure may also be provided bysoftware in cooperation with hardware.

In addition, the functional blocks used in the descriptions of theembodiments are typically implemented as LSI devices, which areintegrated circuits. The functional blocks may be formed as individualchips, or a part or all of the functional blocks may be integrated intoa single chip. The term “LSI” is used herein, but the terms “IC,”“system LSI,” “super LSI” or “ultra LSI” may be used as well dependingon the level of integration.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor otherthan an LSI. After fabrication of LSI, a field programmable gate array(FPGA), which is programmable, or a reconfigurable processor whichallows reconfiguration of connections and settings of circuit cells inLSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology and/or the like.

This disclosure can be applied to a method for formatting andtransmitting resource assignment information in a wirelesscommunications system.

What is claimed is:
 1. An integrated circuit, comprising: at least oneinput, which, in operation, inputs a signal, and circuitry, which, inoperation, controls: receiving a signal that contains a preamble and adata field, the preamble including a common field and a user specificfield; and decoding at least a part of the data field based on thepreamble, wherein a resource assignment subfield in the common fieldindicates a plurality of resource units (RUs) in a frequency domain, andthe user specific field includes a plurality of user fields, each of theplurality of RUs being allocated to a user field or a group of userfields for multiuser-multiple input multiple output (MU-MIMO)transmission in the plurality of user fields, respectively, and theordering of the plurality of user fields in the user specific field isdetermined based on the resource assignment subfield such that the userfield and the group of user fields in the plurality of the user fieldsare in order of increasing frequency of the respective allocated RUs. 2.The integrated circuit according to claim 1, wherein each of theplurality of the user fields contains a user identifier.
 3. Theintegrated circuit according to claim 1, wherein each of the pluralityof RUs is formed of a subset of a plurality of tones that are identifiedby tone indices in the frequency domain.
 4. The integrated circuitaccording to claim 3, wherein each of the plurality of RUs is specifiedby a start tone index and an end tone index of the subset of theplurality of tones.
 5. The integrated circuit according to claim 1,wherein the plurality of user fields include a first user field and asecond user field, and a start tone index of a first RU corresponding tothe first user field is next to an end tone index of a second RUcorresponding to the second user field.
 6. The integrated circuitaccording to claim 1, wherein an unused RU of the plurality of RU isindicated by dummy information.
 7. The integrated circuit according toclaim 1, wherein the preamble includes a first channel field for a firstsubband channel and a second channel field for a second subband channel.8. The integrated circuit according to claim 7, wherein the firstchannel field includes the common field and the user specific field, andthe second channel field includes another common field and another userspecific field.
 9. The integrated circuit according to claim 1, whereinthe common field includes a center RU subfield indicating whether acenter type RU is allocated.
 10. The integrated circuit according toclaim 9, wherein the center type RU corresponds to a last user field ofthe plurality of user fields.
 11. The integrated circuit according toclaim 1, wherein a RU assignment of the plurality of RUs is determinedbased on quality information of the plurality of RUs.